This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Understanding the function of retroviruses is critical in seeking treatment or prevention of HIV. The specific aims for this project include: (1) defining the interaction of Gag with the cytoskeletal motor machinery, (2) determining the role of viral and cellular components in the transport of capsids from the site of assembly to the plasma membrane, (3) defining the interactions of capsids with the ESCRT machinery of the cell and (4) investigating the myristyl switch mechanism that is involved in virus budding.This year we have developed a functional Gag-GFP expressing provirus, as well as an Env (glycoprotein)-Cherry construct that allows us to follow virus capsid assembly and transport, and interactions between capsids and the envelope glycoprotein in real-time by video microscopy. We have shown that the kinetics of intracellular transport of capsids is dependent on both the presence of the viral glycoprotein and cytoskeletal elements in the cell. Disruption of microtubules results in a rapid arrest in capsid transport, that slowly recovers through an unknown mechanism. We showed previously that M-PMV can be inhibited by new world monkey TRIM-5a proteins. We have now characterized the differential evolution of the genes in the TRIM5/6/22/34 gene cluster at the genomic sequence level, (2) demonstrated differential regulation of these genes as a consequence of the changes. We have found that, there is significantly more change in the genomic sequences of TRIM5 and TRIM22 genes compared to TRIM6 and TRIM34. The main characteristic of this change is fixation of transposable elements into the intronic regions of these genes. One such LTR in TRIM22 provides for p53 responsiveness of TRIM22 in Old World primates (humans and rhesus macaques), while New World primates (squirrel monkeys) whose TRIM22 lack this LTR are unable to upregulate TRIM22 following p53 stimulation. Thus the LTRs that have become fixed in the introns of TRIM5 and TRIM22 may allow for differential expression patterns of these genes.